Horticultural crops undergo various physiological and biochemical changes that lead to undesirable physiological disorders, decay and subsequent economic losses during storage. Quality degradation of horticultural crops is mainly caused by postharvest pathogens such as Botrytis cinerea and Penicillium spp., etc. The application of synthetic fungicides remains the most effective method to control postharvest pathogens. However, their use is becoming increasingly restricted internationally due to health concerns and consumers’ requests for safe and natural alternatives. This has led researchers to investigate natural flora as one of the alternatives to be used in crop protection and preservation. Various medicinal plant parts have different phytochemicals and antioxidants that can be used in crop protection and preservation. Extracts from plants such as Ruta chalepensis, Eucalyptus globulus, etc., have proven to be effective in controlling postharvest pathogens of horticultural crops and increased their shelf life when used as a substitute for synthetic chemicals. Furthermore, extracts from neem and other medicinal plants contain a predominant and insecticidal active ingredient. The application of medicinal plant extracts could be a useful alternative to synthetic chemicals in the postharvest protection and preservation of horticultural crops. This review paper details the application of medicinal plant extracts for postharvest protection and preservation of horticultural crops.

Restricted postharvest application of synthetic fungicides in maintaining the quality of citrus fruits has led to a search for alternative postharvest treatments. This study evaluated the efficacy of gum arabic (GA) enriched with green synthesized zinc oxide nanoparticles (ZnO-NPs) in maintaining the postharvest quality of mandarin (cv. Kinnow). ZnO-NPs were synthesized using Bidens pilosa leaf extract and incorporated into GA (2% w/v) at 0, 0.25, 0.5, and 1% to form composite coatings: GA, GA + ZnO-NP 0.25%, GA + ZnO-NP 0.5% and GA + ZnO-NP 1%, respectively. Fruit were dipped for 3 min in the respective coatings, with untreated fruit used as control. Fruit were air-dried, packed in commercial cartons, and stored at 5 ± 1°C and 90 ± 5% relative humidity (RH) for 40 days and observed at 10 days intervals, plus 5 days at 20 ± 5°C and 65 ± 5% RH to determine the incidence of physiological disorders. GA + ZnO-NP showed promise as an alternative postharvest treatment for controlling postharvest physiological disorders associated with ‘Kinnow’ mandarin. For instance, GA + ZnO-NP 0.5% markedly minimized weight loss (9.2%), electrolyte leakage (43.8%) and chilling injury incidence (5.4%) compared to control (weight loss; 33.3%, electrolyte leakage; 90.3% and chilling injury incidence; 41.5%) at the end of the storage. GA + ZnO-NP 1% significantly alleviated rind pitting, with 13.2% incidence compared to 45.2% rind pitting incidence in the control fruit. This was due to significantly higher phytochemical and antioxidant capacity and reduced antioxidant enzyme degradation in coated fruit than in control. In conclusion, gum arabic coating enriched with ZnO-NPs at concentrations between 0.5 and 1% is recommended as a viable option to maintain the quality of ‘Kinnow’ mandarin fruit during cold storage.

Indigenous fruit and nut tree crops are very important to the human diet and subsequent food security and income generation in the Kingdom of Eswatini. Indigenous fruits and nuts are important for the nutritional contribution as sources of Vitamins and minerals. They also provide fibre which is essential for proper digestion of food. Fruits, particularly nuts provide man with unsaturated fats which are good for the heat and the cardio vascular system. Indigenous fruits and nuts are aesthetic as they provide interesting colour, texture and variety. Despite the immense benefits of indigenous fruits and nuts to the people of the Kingdom of Eswatini, there has not been enough effort put towards domesticating the indigenous fruit and nut trees and subsequent commercialising their products. The objective of this paper was to document strategies towards domestication and commercialisation of indigenous fruits and nuts for improved livelihoods of Emaswati citizens, which in turn will help achieve sustainable development goals (SDGs) pertaining to human health and food security in the Kingdom of Eswatini. It can be concluded that domesticating indigenous fruit and nut trees can be achieved through a multi-stakeholder involvement. Domestication can also help in conservation of indigenous fruit and nut trees. Value addition on indigenous fruits and nuts can generate more income.

Calcium (Ca2+) related physiological disorders of fruits and vegetables are abnormalities of fruits and vegetables which are not caused by infectious diseases, insects, nematodes or animals. Fruit and vegetable abnormalities occur due to environmental stress, nutritional deficiencies or excess on the plant. In this study, information was sought through informal surveys, review of literature and interviews with key post-harvest handling and storage participants and direct observation of fruits and vegetables in the markets. Calcium related post-harvest physiological disorders of fruits and vegetables encountered in this study included: cavity-spot, black end and cork, bronzing, skin freckles, fruit and crown, fasciation, soft-nose/spongy-tissue, granulation, low temperature breakdown/flesh browning, water-core, senescent-breakdown, superficial-scald, bitter pit, leaf tip-burn, golden specks and blossom-end rot. Post-harvest physiological disorders result in direct economic losses and pose a threat to food and nutritional security. Various ways of alleviating particular Ca2+ related post-harvest related physiological disorders are suggested e.g. addition of Ca2+ containing fertilisers and Ca2+ sprays.

Decline in the availability of suitable land and good fertile soil for vegetable production due to climate change, urbanisation and increasing population has resulted in studies to find alternative media that can be used to grow high value crops such as Swiss chard. The experiment was conducted at the Horticulture Department Greenhouses of the University of Eswatini, Luyengo Campus to determine the growth and yield of Swiss chard using different growing media. The treatments were laid out in a Randomised Complete Block Design (RCBD) and replicated four times. The media treatments consisted of sand, sawdust and mixture of sand and vermiculite (1:1). The results showed that Swiss chard grown in sawdust performed better than those in the other growing media and gave significantly (P<0.05) higher fresh yield (227.7 g/plant), root length (25 cm/plant) and the highest chlorophyll content (48.9µmol m2). Plants grown using sand had the lowest fresh yield (58.3 g/plant), root length (11.9 cm/plant) and the chlorophyll content (17.49 µmol m2). The results showed that Swiss chard production in hydroponics using sawdust resulted in higher yields and therefore should be recommended to farmers for use. Not only is it the best in production of Swiss chard but it is also readily available at low cost and re-usable provided it is treated. Keywords: Growing media, hydroponics, Swiss chard, food and nutritional security, sustainable development goals (SDGs), climate-smart agriculture